SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb53db093f80498b45017b30ea4d87279b2748c12f8e1bd01263f395e65a8e50' 
  AND token = 'F+vYoNKt3AEPPtdXPzG2FXSjU9Ywk4k/swzlZiWK+ws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}